Title: Chloride Induced Steel Corrosion in Concrete: Part 2—Gravimetric and Electrochemical Comparisons

Author(s): Daksh Baweja, Harold Roper, and Vute Sirivivatnanon

Publication: Materials Journal

Volume: 96

Issue: 3

Appears on pages(s): 306-313

Keywords: blast furnace; slag; chlorides; corrosion; marine atmosphere

DOI: 10.14359/627

Date: 5/1/1999

Abstract:
This is the second of a two-part paper covering research into chloride induced steel corrosion in concrete. Work described in this paper focused on relationships between electrochemical data on chloride induced reinforcement corrosion and gravimetric steel weight losses. Data were collected on a series of reinforced concrete slabs that were partially immersed in 3 percent NaCl solution for a period of 5 years. Reinforced concrete slabs investigated were made at a range of water-binder ratios with portland cements having high and low C3A contents, a slag blended cement, or a fly ash blended cement. Data in this paper focus on measurements over time of concrete resistivity, corrosion rates, and gravimetric weight losses of steel taken at the end of the exposure period. Rates of corrosion of steel in concrete were measured using potentio-dynamic anodic procedures. An analysis of estimated corrosion currents Ic and the area under the Ic versus time envelope Acr for reinforcement within concrete slabs used in the investigation is described. Measurements of weight loss of steel through corrosion in concrete are analyzed and related back to the electrochemical measurements taken. It was found that concrete water-binder ratio highly influenced the corrosion rate of steel in concrete. Quantitative links between steel weight loss, the electrochemical data, and concrete resistivity have been found. Under high chloride conditions, the blended cement concretes having low water-binder ratios were found to perform better than other concretes investigated in this study. The data suggests that such concretes had higher resistivity characteristics, lower corrosion rate characteristics, and were likely to result in lower reinforcement weight losses when compared with equivalent portland cement concretes. Reinforced concrete performance under the high chloride conditions did not reflect concrete strength data for the materials considered. The results serve to provide some guidelines for the design of concrete structures for ensuring durability.